When video is streamed over the Internet and played back through a Web browser or media player, the video is delivered in digital form. Digital video is also used when video is delivered through many broadcast services, satellite services and cable television services. Real-time videoconferencing often uses digital video, and digital video is used during video capture with most smartphones, Web cameras and other video capture devices.
For standard dynamic range (“SDR”), digital video represents common colors in a relatively narrow range of brightness. Brightness can be measured in candelas per square meter (cd/m2), which indicates luminous intensity per unit area. This unit of luminous intensity per unit area is called a “nit.” A typical SDR display device may represent colors from pale colors through colors that are relatively vivid, in a brightness range from 0 nits to 100 nits. More recently, display devices having high dynamic range (“HDR”) have been introduced. A typical HDR display device may represent colors in a wider color gamut (potentially representing colors that are more vivid or saturated) and in a larger brightness range (e.g., up to 1500 nits or 4000 nits). Video produced for playback on an HDR display device can have an even larger brightness range (e.g., 0 nits to 10,000 nits).
When HDR content is played back on an SDR display device, details in moderately bright sample values and very bright sample values are lost. For example, bright sample values above a certain threshold value (e.g., 100 nits) are clipped to the brightest sample value possible for the SDR display device, or bright sample values above a certain threshold value (e.g., 95 nits) are compressed to a very small range, so that a very wide range of bright sample values in the HDR content is represented with a small range of values on the SDR display device. On the other hand, when HDR content is played back on an HDR display device, the HDR display device can potentially display sample values in its full brightness range. In many cases when HDR content is played back on an HDR display device, however, the full brightness range is not needed.